The US government said BP's ruptured well in the Gulf of Mexico gushed an estimated 4.9 million barrels of oil, making it the largest accidental oil spill of all time.

The US government said BP's ruptured well in the Gulf of Mexico gushed an estimated 4.9 million barrels of oil, making it the largest accidental oil spill of all time.

"Overall, the scientific teams estimate that approximately 4.9 million barrels of oil have been released from the well," the joint response command that includes BP and the US government said in a statement on Monday describing the new estimate.

"Not all of this oil and gas flowed into the ocean; containment activities conducted by BP under US direction captured approximately 800,000 barrels of oil prior to the capping of the well," they said.

The 4.9 million barrels is at the upper end of an earlier official estimate, which said that between 3.0 million and 5.3 million barrels had spewed from the well between April 20, when the BP-leased Deepwater Horizon rig exploded, and July 15, when a cap placed over the wellhead was finally sealed.

The refined estimates "are the most accurate to date and have an uncertainty of plus or minus 10 per cent," according to the statement.

The 4.1 million uncontained barrels estimated to have spewed into the water make the spill the biggest accidental oil disaster in the history of the petroleum industry, and second only to the intentional release of crude by Iraqi forces during the 1991 Gulf War.

The previous largest accidental spill was a 1979 disaster-- also in the Gulf of Mexico -- in which 3.3 million barrels gushed from the Ixtoc-1 well after an explosion on a rig operated by Mexican state oil company Pemex.